1. Field of the Invention
This invention generally relates to tire treads, and more particularly relates to monitoring tire treads.
2. Discussion of the Related Art
The handling performance of a motor vehicle (e.g., vehicle steering, braking and fuel consumption) is affected by the condition of the tires. Handling performance can be affected by improper tire inflation, abnormal tire tread wear and out of balance conditions.
It is estimated that ten percent of tires that would normally wear out at 40,000 miles actually wear out at 30,000 miles due to abnormal tire tread wear. As a result, over the course of a vehicle life of 120,000 miles, the vehicle may need an additional set of tires at an average cost of $300. Thus, it is desirable to alert the driver of abnormal tire imbalance.
A tire monitoring system available from SmartTire Systems, Inc. (www.smartire.com) uses wireless technology to monitor the air pressure and temperature in vehicle tires using wireless wheel-mounted sensors and a display receiver mounted within sight and reach of the driver. A sensor is mounted on each wheel and each tire is mounted over the sensor. Each sensor may contain a pressure transducer, a temperature transducer, a centrifugal switch, a radio transmitter and a lithium battery. The display module shows required pressure, actual pressure, pressure status and temperature. While this system provides temperature and pressure information, it does not provide information about tread wear and balance.
In addition, anti-lock braking systems (ABS) and integrated vehicle controllers (IVC) may require the input of information indicating the wheel rotational speed for each wheel. A separate wheel speed sensor may be provided for each wheel. This may typically include a toothed wheel made of a magnetic disk attached co-axially to a corresponding axle rotatably supporting a tire and a pick-up coil arranged adjacent each toothed wheel with an interval therebetween to provide an alternating sensor signal having a frequency indicative of the speed of each tire.
U.S. Pat. No. 6,278,361 discloses a system and method for monitoring vehicle conditions affecting tires including tire tread wear, shock absorber performance, balance condition of the vehicle tire, and rotational speed of a vehicle wheel.
Embodiments of the present invention may provide a tire monitoring method that includes monitoring a parameter of a tire of a vehicle over time and comparing information regarding the monitored parameter (over time) with a reference threshold value of the parameter (over time). The method may also include providing information to a driver based on the comparison. The parameter may be acceleration (axial, radial or longitudinal) along an axis of the tire. The parameter may also be tire imbalance, temperature inside the tire, speed of the tire, load and/or pressure, for example. Information regarding the comparison may be transmitted to a driver if the monitored parameter exceeds the reference threshold value for a predetermined amount of time. This information may be used to detect, monitor or predict tire tread separation.
Embodiments of the present invention may also provide a tire monitoring system that includes at least one sensor to monitor a parameter of a tire of the vehicle, a memory device to receive and store signals from the sensor indicative of the parameter over time, and a processing device to couple to the memory device and to compare information regarding the parameter over time with a reference threshold of the parameter over time. A display device (or audio device, or other type of indicator) may display (or relay) information to a driver regarding the tire. The sensor system may provide a warning indication to the display device if the parameter exceeds the threshold value for a predetermined amount of time. The warning indication may relate to an actual or a predicted tire tread separation.
The sensor may be a radial accelerometer to monitor radial acceleration, an axial accelerometer to monitor axial acceleration and/or a longitudinal accelerometer to monitor longitudinal acceleration. The sensor may further be a tire pressure sensor, a temperature sensor and/or a speed sensor.
Other features of the invention will become apparent from the following detailed description taken in conjunction with the annexed drawings, which disclose preferred embodiments of the present invention.